PROJECT ABSTRACT The incidence of liver cancer is rising because of obesity and metabolic syndrome. Hepatocellular carcinoma (HCC) is a deadly disease with limited treatment options. Using a drug such as sorafenib, liver cancer will never be treated; it can only be controlled by a couple months. Such outcome does not justify its high price, at up to $5,000 per patient per month. An effective cancer treatment strategy should target the pathways by which cancer arises in the first place. It is important to note that the liver is constantly exposed to all types of chemicals generated from the gut because more than 70% of hepatic blood comes from the gut via enterohepatic circulation. Emerging evidence also reveals that gut microbiota are not only implicated in colon cancer, but also affect hepatic inflammation and liver carcinogenesis. The proposed project targets a tumor suppressor i.e. miR-22, which is induced by the beneficial chemicals normally presents in the liver and gut i.e. bile acids (BAs), retinoic acid (RA), and short chain fatty acids (SCFAs) that have HDAC (histone deacetylase) inhibitor property. Thus, using miR-22 and its inducers not only can induce cancer cell apoptosis and arrest, but also provide preventive means to stop cancer reoccurrence leading to an effective treatment strategy. To understand how gut-derived signaling affects liver carcinogenesis, we uncovered that miR-22 is consistently reduced in both HCC and colon cancer specimens. In addition, our novel data also revealed that the expression levels of BA receptor FXR (farnesoid x receptor), SCFA receptors including GPR41, 43, and 109A, as well as ALDH1A1 (aldehyde dehydrogenase 1A1), a RA generator, and CYP26A1, a RA oxidation enzyme, were all reduced in both human HCC and colon cancer specimens. Moreover, FXR knockout mice, which had reduced miR-22 and dysregulated BA synthesis, spontaneously develop liver cancer. Furthermore, our exciting preliminary data revealed that miR-22 is an acetylation modifier as well as cell cycle arrestor due to its ability to reduce HDAC1, HDAC4, SIRT1, and SRC1 as well as CYCLIN A2 proteins. To have a comprehensive understanding of the effect of miR-22 in liver cancer, Aim 1 studies the mechanism by which miR-22 has an anti-cancer property by investigating the downstream effects of miR-22. Aim 2 studies the effect of miR-22 mimics and inhibitors in HCC treatment using an orthotopoic liver cancer model. Aim 3 analyzes the effect of miR-22 inducers including a synthetic FXR agonist obeticholic acid and a combination RA plus a SCFA i.e. propionate in HCC treatment. Additionally, we will study the role of miR-22 by including miR-22 inhibitors or mimics in the treatment. Furthermore, the molecular mechanism by which acetylation mediates the anti-cancer action of miR-22 and it inducers will be analyzed. Based on the promising data generated using liver and colon cell lines, mice, and human specimens, we are confident that the generate data will advance the field of liver cancer treatment.